The present invention relates generally to the art of pin fasteners.
Pin fasteners today have a wide variety of applications, but are extensively used in the aircraft industry, where rather severe strain-resisting capabilities are currently required. Furthermore, as aircraft design becomes more sophisticated, it is evident that fastening devices will be required to perform multiple functions. For instance, fasteners are being utilized to insure fuel tight fits for airplane fuel containers, as well as providing a tension or shear resistant connection between two members which are to be joined in some specified fashion.
Currently, to provide the required fuel and corrosion protection, high strain, flush-headed fasteners having a single, 100-degree included angled head are used in combination with a rubber-based sealant. The sealant provides the fuel seal and corrosion protection for the countersunk fasteners. However, this fastening combination has several disadvantages, including increased labor costs and added weight.
Although the single tapered, 100-degree pin fastener head may in some cases be designed to provide an inherent fuel seal, underhead corrosion still remains a significant problem, because there is not an adequate interference fit between the pin head and the walls of the opening in the member material. Additionally, fatigue failures typically occur in the vicinity of the countersink, thus severely shortening the useful life of the airplane or member combination fastened by the pin.
With respect to the attachment end of prior art pin fasteners, the annular rings currently provided are widely separated, having a ring angle of approximately 45 degrees, and rather large radii of curvature both at the trough of the thread, and at the head of the rings. To allow sufficient room for an appropriate number of the annular rings to be placed on a pin for tension strength, while maintaining the pin's overall weight at a minimum, the length of the shank portion of the bolt is decreased, thus severely reducing the shear strength of the pin-pin collar combination. The prior art has thus been forced to utilize one pin configuration for shear strength, and another configuration for tension strength.
The present invention, however, significantly reduces these problems, insofar as it is a double tapered wedge head bolt, having the capability of providing an adequate fuel seal and corrosion-free fastening without the use of sealants, as well as having the capability of withstanding both large shear and tension forces with minimum weight.
In accordance with the above, it is a general object of the present invention to provide a pin fastener which overcomes the disadvantages of the prior art.
It is another object of the present invention to provide a pin fastener which is capable of a controlled interference fit and which has a high resistance to tension forces.
It is a further object of the present invention to provide a pin fastener which is inherently capable of providing a fuel seal without the use of additional sealants.
It is a still further object of the present invention to provide a pin fastener having a controllable interference fit.
It is a further object of the present invention to provide a pin fastener having sufficient head interference to resist underhead corrosion.
It is a still further object of the present invention to provide a combination of work members and pin fastener such that fatigue life of the pin is increased.
It is yet another object of the present invention to provide a pin fastener which is capable of withstanding both high shear and high tension stresses.
Other and further objects, features and advantages of the invention will become apparent as the description proceeds.